Power transmission systems are formed of a complex interconnected system of generating plants, substations, and transmission and distribution lines. A significant issue currently plaguing power transmission systems may be characterized as geomagnetically-induced currents (GICs), which are currents induced in a power line due to time-varying magnetic fields external to the Earth and resulting time-varying magnetic fields along the Earth's surface. The time-varying magnetic fields external to the Earth often result from solar activity and the activity of other extra-terrestrial objects.
These GICs have been measured as high as 100 amps for a 20 minute duration. They are typically in a much lower frequency range than the 50-60 Hz AC power that is conducted on power lines in modern power transmission systems. These GICs typically have such low frequency as to be quasi-DC currents. Unfortunately, modern transmission systems do not handle DC currents well. For example, high DC currents may cause undesirable resistive heating of components such as transformer windings which can cause such components to fail and result in a partial failure of the power transmission system. Prior art systems for measuring GICs can be bulky, expensive, and require major efforts to be installed. In many cases, this is because the GIC sensor requires a break in the power line in order to install same.
It is against this background that the techniques disclosed herein have been developed.